A variety of therapies exist for treating patients with implantable infusion systems. The implantable infusion systems can be used to deliver therapeutic fluids to a target location of a patient, such as the spinal canal, the brain, or the heart. The implantable infusion systems include implantable infusion devices that are often subcutaneously implanted in a convenient location in the patient and implantable catheters that are used to carry the therapeutic fluids from the infusion device to the target location.
Implantable infusion devices can have refillable reservoirs for housing the therapeutic fluids, which can be infused over time. The reservoirs can be periodically refilled so that the implanted infusion systems can be employed for long-term use. Typically, the infusion devices have a fill port in communication with the reservoir. A refill apparatus needle can be percutaneously inserted into the fill port so that fresh therapeutic fluid can flow through the refill needle into the port to refill the reservoir and replenish the supply of therapeutic fluid.
Because the device is implanted within the patient and cannot be seen directly, care must be taken to ensure that the needle is properly placed into the port before transferring the therapeutic fluid. If the needle is not properly located within the fill port, the therapeutic fluid may be inserted into a subcutaneous pocket of the patient rather than into the reservoir of the implanted infusion device. Accordingly, efforts have been made to identify to a clinician the location of the fill port relative to the patient's skin prior to insertion of the refill needle. For example, templates are well known, and can provide a general indication or map of the port assembly location following palpating the device's periphery through the patient's skin. Additionally, electronic or magnetic systems have been suggested that provide the clinician with additional information generally indicative of the port position. Once the clinician arrives at an initial estimation of port location, upon inserting the needle through the patient's skin, the clinician normally can make a manual tactile determination as to whether the needle tip has been correctly directed to the appropriate port and has subsequently pierced through a septum covering the port. Most clinicians are relatively comfortable in making this determination as, based on experience; the clinician can tactilely sense or feel when the needle has been inserted through the septum. As such, accidental subcutaneous “pocket fills” are rare.